Update token_source.go

[eltociear]

Why are the changes needed?

minor fix

What changes were proposed in this pull request?

How was this patch tested?

Setup process

Screenshots

Check all the applicable boxes

• I updated the documentation accordingly.
• All new and existing tests passed.
• All commits are signed-off.

Related PRs

Docs link

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 61.99%. Comparing base (2f1f813) to head (b4d276c).
Report is 10 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5396      +/-   ##
==========================================
+ Coverage   61.08%   61.99%   +0.90%     
==========================================
  Files         793      611     -182     
  Lines       51156    36375   -14781     
==========================================
- Hits        31251    22550    -8701     
+ Misses      17033    11860    -5173     
+ Partials     2872     1965     -907     

Flag	Coverage Δ
unittests-datacatalog	69.31% <ø> (ø)
unittests-flyteadmin	?
unittests-flytecopilot	17.79% <ø> (ø)
unittests-flytectl	68.31% <ø> (ø)
unittests-flyteidl	79.30% <ø> (ø)
unittests-flyteplugins	61.94% <ø> (ø)
unittests-flytepropeller	57.32% <ø> (ø)
unittests-flytestdlib	65.75% <ø> (ø)

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